1. Field of the Invention
The present invention relates to a toner used for developing latent electrostatic images in electrophotography, a latent electrostatic recording method, a latent electrostatic printing method, or the like, and also relates to a developer, a toner container, a process cartridge, an image forming method, and an image forming apparatus all of which utilizes the toner.
2. Description of the Related Art
In electrophotography, a latent electrostatic image is formed on a latent electrostatic image bearing member (also referred as to “image bearing member” or “photoconductor” hereinafter) by charging and partially exposing the image bearing member, and thereafter the latent electrostatic image is developed using a developer containing a toner to thereby form a toner image. This toner image is transferred onto a recording medium, and then fixed. In the mean time, the toner remained on the image bearing member without being transferred to the recording medium is cleaned by means of a cleaning member such as a blade disposed so as to contact with a surface of the image bearing member with a certain pressure.
As one of manufacturing methods of the toner, a pulverization method has been known. The pulverization method is a method in which a toner is manufactured by melting and mixing toner components which contain a thermoplastic resin as a binder resin added with a coloring agent and optionally additives, pulverizing the mixture, and then classifying the pulverized products. The toner obtained from this method has shortcomings such that a diameter of the particles becomes large, and thus high-quality images cannot be provided.
In order to overcome the shortcomings of the pulverization method, there has been proposed a method for producing a toner using a polymerization method and an emulsion-dispersion method. As the polymerization method, a suspension-polymerization method, an aggregation method, and the like are known. The suspension-polymerization method is a method in which monomers, a polymerization initiator, a coloring agent, a charge controlling agent, and the like are added to an aqueous medium containing a dispersant while stirring to thereby obtain oil droplets, and then the oil droplets are polymerized to produce a toner. The aggregation method is a method in which particles obtained by emulsion-polymerization or suspension-polymerization are aggregated, and then fused to produce a toner. These methods realize the downsizing of the particle diameter of the toner, but a material for use as a main component of the binder resin is limited to polymers obtainable from radical polymerizations. Therefore, there is still a shortcoming such that a toner cannot be produced using, as a main component of the binder resin, polyester, epoxy resin, or the like which is suitable for the production of a color toner.
Under considering these circumstances, there have been proposed methods for producing a toner using an emulsion-dispersion method wherein a mixture containing a binder resin, a coloring agent, and the like is mixed with an aqueous medium and then emulsified so as to produce a toner (refer to Japanese Patent Application Laid-Open (JP-A) Nos. 05-66600 and 08-211655). According to these proposed methods, a toner having a small particle diameter can be attained while maintaining the varieties of usable binder resins therefore. However, there are problems in the emulsion-dispersion methods such that fine particles are formed, and a loss is made in emulsification.
There has been also proposed methods for producing a toner wherein polyester is emulsified and dispersed to produce particles, and the obtained particles are aggregated and fused to produce a toner (refer to JP-A Nos. 10-020552 and 11-007156). According to these proposed methods, the generation of fine particles can be prevented, and thus the loss made in emulsification can be reduced.
Moreover, the toner obtained from the polymerization method and the emulsification-dispersion method tends to have a spherical shape due to surface tension of droplets generated in the dispersion process. Therefore, in the case where a toner is used in an apparatus utilizing a blade cleaning system, the spherical toner is rolled between the cleaning blade and the photoconductor and goes into the space between the cleaning blade and the photoconductor, and thus it is difficult to clean.
There has been also proposed a method for obtaining aggregated particles having a particle diameter of 5 μm to 25 μm wherein particles are aggregated by using polyvinyl alcohol having a certain saponification degree as a dispersant (refer to Japanese Patent (JP-B) No. 2748419). However, the aggregated particles obtained in this manner tend to have a large particle diameter.
Moreover, there has been proposed a method for deforming particles by adding toner components in an organic solvent together with filler (refer to JP-A No. 2005-49858). However, in this method, a viscoelasticity of the toner is reduced as a result of the addition of the filler, and thus the low temperature fixing is inhibited. In the case where the filler is locally positioned on the surface of the toner, bleeding of wax or a binder resin is inhibited by the filler, and thus low temperature fixing ability and hot-offset resistance are degraded.
It has been also developed a charge controlling agent wherein ions such as metal cations present between layers of a layered inorganic compound are modified with ions such as organic cations, and has been proposed a use of such the charge controlling agent in a toner for electrophotography (refer to JP-A Nos. 2003-515795, 2006-500605, 2006-503313, and 2003-202708). There has been also proposed a method wherein organic ions are made intercalating between layers of a layered inorganic compound (refer to JP-A No. 05-57288). Moreover, there has been proposed to improve capability of a layered inorganic compound to an organic solvent by intercalating certain organic ions having a polyoxypropylene group to thereby attaining stable thickening effect towards a certain organic solvent for a long period (refer to JP-B No. 3502993).
However, there have not been provided or proposed a toner which excels in low temperature fixing, is capable of forming high quality image, and has stable cleaning properties for a long period, and related technologies thereof. Therefore, there are strong demands for further improvements or developments of such the toner and related technologies.